Devices for the production of copies



Dec. 7, 1965 G. CRANSKENS ETAL 3,

DEVICES FOR THE PRODUCTION OF COPIES Filed July 20, 1962 lNVENfOPj:

Georg CRANSKENS Uwe THURAT United States Patent 3,221,621 DEVICES FOR THE PRODUCTION OF COPIES Georg Cranskens, Wedel, Holstein, and Uwe Thurat, Hamburg, Germany, assignors to Lumoprint Zindler K.G., Hamburg, Germany, a corporation of Germany Filed July 20, 1962, Ser. No. 211,361 Claims priority, application Germany, July 26, 1961, L 39,624 7 Claims. (Cl. 951.7)

Our present invention relates to an apparatus for reproducing the contents of an original or master sheet on a photosensitive copy sheet provided with an electrophotogr'aphic surface layer.

In such systems it is necessary to subject the copy sheet, prior to its exposure, to an electric field by moving the sheet past a set of charging electrodes and, immediately thereafter, to expose the photosensitive layer of the charged sheet to light rays from the original whereby a latent image is produced in that layer. This image is subsequently devolped, e.g. by magnetic application of a suitable powder to the layer surface, whereupon the image is fixed by fusion of the developer powder onto the layer.

The general object of our invention is to provide means for performing the charging operation in an expeditious manner and within a restricted area of the guide path for the copy sheet whereby the overall arrangement can be made more compact than with prior devices of this type.

A more particular object of our invention is to provide combined guiding and charging means for the copy sheet adapted to direct the latter along a curved path, it being thus possible to charge the electrophotographic surface layer at a location at which the copy sheet is deflected by a transport roller on its way from an inlet slot to an exposure station.

A further object, allied with the preceding one, is to provide guide and charging means of this character adapted to be positioned adjacent the lower surface of a transport roller.

It is also an object of our invention to provide improved guiding means insuring the substantially uniform exposure of the entire sheet surface to a charging potential while effectively shielding the sheet from the potential source.

The-foregoing objects are realized, in accordance with our present invention, by the provision of a guide unit in the form of a perforated plate or grid member of nonconductive material, positioned to be contacted by the electrophotographic layer of a copy sheet as it is moved past a source of charging potential, this member being fixedly interposed between the sheet and the potential source; advantageously, the grid is formed with slots which are inclined with,' reference to the direction of sheet motion and define between them an array of preferably foil-shaped bars, the spacing and inclination of the bars being so chosen that the combined slot width in the direction of sheet motion is substantially constant throughout the region of the slots. The grid or plate member may be coaxially curved about the periphery of an associated feed roller juxtaposed therewith, particularly about the underside of that roller, to define part of the guide path for the copy sheet.

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Further advantages and features of the 'invention'will be evident from the following description of a representative embodiment schematically illustrated in the drawing, in which:

FIG. 1 shows a schematic side view of an exposure device according to the invention;

FIGS. 1A and 1B are fragmentary elevational views similar to FIG. 1, showing partial modifications;

FIG. 2 shows an enlarged plan view of a guide unit forming part of the system of FIG. 1; and

FIG. 3 is a diagram of the drive and control circuit of the device shown in FIG. 1.

In FIG. 1 an inlet slot 2 for the copy sheet and an adjacent inlet slot 3 for the original or master sheet are provided in the side wall of a housing 1. The copy sheet is guided by a central guide element 4 to a transport and pressing roller 5 which is juxtaposed with a transparent exposure plate 6, and the original is guided to a transport and pressing roller 7, arranged next to a transparent illumination plate 8. Guide rollers 9 and 10 are associated with the transport and pressing rollers. The exposure device includes two light sources 11 and 12, for illumination of the original via transparency 8, and an objective 13 by which the light rays are focused upon the copy sheet behind transparency -6. The original or master sheet is conveyed by a guide element 14 to the illumination plate 8 and is then advanced on the guide element 15 by the transport and pressing roller to the outlet slot 16.

The copy material is directed by a guide unit 17 to the exposure plate 6 and therefrom past transport rollers 18 and guide elements 19 into a treatment section, indicated as a whole by reference numeral 20, in which a developer station 21 and a fixing station 22 are provided. This treatment section terminates at an outlet slot 23 for the copy material.

Charging electrodes 24 are provided beneath the guide unit 17 and are screened by insulating walls 25 from the remaining parts of the apparatus, the wire-shaped electrodes being equidistant from the proximal convex side of member 17. The charging takes place through the unit 17. The guide unit 17 preferably comprises two sets of parallel bars or sheets of an electrically nonconductive material diverging in the direction of advance as more fully described with reference to FIG. 2.

It is an essential feature that the guide unit 17 is juxtaposed with a transport means which effects the advance of the copy material in the vicinity of the guide unit. In the preferred embodiment illustrated, the guide unit 17 is curved substantially coaxiall-y with the roller 5 representing the transport means.

However, as shown in FIG. 1A, a flat guide unit 17a with chargingelectrodes 2411, over which extends a pressing and transport roller 5a, may alternatively be provided in place of the guide unit'17. The guide unit may also be arranged, as shown for example at 17b in FIG. 1B, above the transport roller 5b, the latter advantageously being elastic and able to effect a uniform pressing in accordance with the thickness of the copy material; the charging electrodes have been designated 24b in FIG. 1B. In the case where the guide element has a concave side coaxial with the transport roller, as in the system of FIG. 1, the copy material is transported in spite of the illustrated separation between the two members, since, on account of its inherent stiffness 'it presses against the periphery of the transport roller 5 so that the latter can exert a frictional force thereon.

In FIG. 2 there is illustrated a particularly advantageous construction of the guide unit 17. This comprises a grid-shaped plate 26 which has a substantially triangular, preferably V-shaped central opening 27 flanked on each side by slotlike openings 28 diverging in the direction of feed, together with further edge openings 29. The V-shaped opening 27 is defined on one side by a substantially triangular tongue 27; suitably disposed. somewhat below the plane of the array of foil-shaped bars 42, 42' between the openings 28 so that there is no danger that a copy sheet advancing from the bottom as shown in FIG. 2 can pass beneath the tongue 27.

The charging potential of energized electrodes 24 is effective through the plate 26 which constitutes a compact guide for the copy paper to be charged.

The guide plate 26 may comprise for example plastic material.

The two sets of bars 42, 42 defined by the slots 27, 28 and 29 are so spaced and inclined that the length of each slot or the combined lengths of a pair of adjoining slots in the direction of sheet motion is substantially constant throughout the width of the slotted portion of plate 26. Thus, the distance x at the center of the plate, measured between the tip of tongue 27' and the bottom of the V-shaped central slot 27, is the same as the similarly designated length of a line L intercepted by one of the slots 28. Another line L which cuts through adjacent slots 27 and 28, has intercepted sections of lengths y and z which add up to the distance x. This relationship is brought about by the alignment of the upper corners Z of any trapezoidal slot 28 with the proximal lower corner Z of an adjacent slot in the direction of advance, as indicated along the line L This arrangement insures that each region of the sensitive layer is exposed to the charging potential of electrodes 24 for the same length of time.

The provision of two diverging sets of parallel bars 42 and 42', defined if desired by slots as illustrated in FIG. 2, has the advantage that the copy material entrained by the associated transport device is also smoothed by the application of an outwardly acting force to it.

Conventional ventilation slots 30, here defined by downwardly and rearwardly inclined slats 31, are provided above the fixing device 22. Heat can escape easily through these openings.

All rotating parts are supported in a manner not shown in the side or intermediate walls of the housing which extend parallel to the plane of FIG. 1. At least at one side there is disposed a chamber for accommodating drive and connection units. In addition, transmissions and linkages between the individually driven parts are provided in this chamber. The driving directions are indicated in each case by arrows. Illustration of the drive and connection elements has been omitted from FIG. 1 for the sake of clarity.

FIG. 3 shows the drive means and connection devices energized from a power supply or voltage source 31. A circuit 33 is connected to the power supply 31 by a double-pole switch 32. In this circuit an exposure light source, consisting of the lamps 11 and 12, and a transformer 34 are connected in parallel, a charging station 35 including the wire-type electrodes 24 being connected to the transformer 34. A further circuit 36, connectable to the voltage source 31 by a double-pole switch 37, serves to energize a motor 38. This motor drives a multistage transmission 40. The rollers 5 and 7 are driven for example via an intermediate gearing 40'. Roller pairs 18 and 39 (disposed in the guide path for the copy sheet terminating at the outlet slot 23 in FIG. 1) and a pin roller 41 (between stations 21 and 22) can be driven directly from transmission 40, the respective transmission ratios being selected for suitable drive speeds.

The transmissions can be constructed as gear trains, chains or belts and, in a manner usual in such apparatus, are arranged in a side chamber outside the treatment space, an intermediate wall between this chamber and the chamber space having supports through which the shafts extend.

We claim:

1. In an apparatus for reproducing the contents of an original on a photosensitive copy sheet provided with an electrophotographic surface layer, in combination, guide means for directing an unexposed copy sheet along a predetermined path toward an exposure station, said guide means including a stationary perforated plate of nonconductive material; charging-electrode means for said layer including a plurality of elongated conductors disposed close to said path but separated therefrom by said plate; and feed means including a roller juxtaposed with said plate for advancing the copy sheet along said path with said layer contacting said plate in the region of said charging-electrode means, said conductors being substantially equidistant from said plate.

2. In an apparatus for reproducing the contents of an original on a photosensitive copy sheet provided with an electrophotographic surface layer, in combination, guide means for directing an unexposed copy sheet along a predetermined path toward an exposure station, said guide means including a stationary perforated plate of nonconductive material; charging-electrode means for said layer including a plurality of elongated conductors disposed close to said path but separated therefrom by said plate; and feed means including a roller juxtaposed with said plate for advancing the copy sheet along said path with said layer contacting said plate in the region of said charging-electrode means, said plate being curved substantially coaxially about the periphery of said roller, said conductors being substantially equidistant from said plate.

3. In an apparatus for reproducing the contents of an original on a photosensitive copy sheet provided with an electrophotographic surface layer, in combination, guide means for directing an unexposed copy sheet along a v predetermined path toward an exposure station, said guide means including a stationary plate of nonconductive material having slots inclined with reference to the direction of sheet motion, the combined slot length in said direction of sheet motion being substantially constant throughout the width of the slotted plate portion; charging electrode means for said layer disposed close to said path but separated therefrom by said plate; and feed means for advancing the copy sheet along said path with said layer contacting said plate in the region of said charging-electrode means, said plate being cylindrically curved with its convex side turned toward said charging-electrode means, the latter comprising a plurality of elongated conductors substantially equidistant from said convex side.

4. The combination defined in claim 3 wherein said plate is divided by said slots into two sets of parallel bars diverging in the direction of sheet motion.

5. In an apparatus for reproducing the contents of a master sheet on a photosensitive copy sheet provided with an electrophotographic surface layer, in combina tion:

a housing having a side wall provided with inlet means for said sheets;

first transport means including a lower roller for conveying said master sheet along a lower guide path past an illuminating station;

second transport means including an upper roller above said lower roller for conveying said copy sheet along an upper guide path past an exposure station; guide means juxtaposed with the underside of said upper roller for holding said copy sheet in contact therewith, said guide means including a stationary perforated plate of nonconductive material;

and chargingelectrode means for said layer disposed References Cited by the Examiner close to the surface of said upper roller but sepa- UNITED STATES PATENTS rated therefrom by said plate, said charging-electrode 2 234 717 3/1941 Altman et a1 88*24 means comprising a plurality of elongated conduc- 2863063 12/1958 Schulze "i6 5 X tors substantially equidistant from said plate. 5 2:868:989 1/1959 Haacke 6- 'lhe Combination defined in claim 5 h r ln 53 d Limberger plate 15 provided wlth slots inclined with reference to the 3,088,386 5/1963 Sugarman directifin of Sheet motion- 3,101,034 8/1963 Salger 95 77.5

7. The combination defined in claim 6 wherein the combined in length of said slots in the direction of sheet 10 FOREIGN T motion is substantially constant throughout the Width of 648,116 12/1950 Great B l a the slotted plate portion. EVON C. BLUNK, Primary Examiner. 

1. IN AN APPARATUS FOR REPRODUCING THE CONTENTS OF AN ORIGINAL ON A PHOTOSENSITIVE COPY SHEET PROVIDED WITH AN ELECTROPHOTOGRAPHIC SURFACE LAYER, IN COMBINATION, GUIDE MEANS FOR DIRECTING AN UNEXPOSURE STATION, SAID A PREDETERMINED PATH TOWARD AN EXPOSURE STATION, SAID GUIDE MEANS INCLUDING A STATIONARY PERFORATED PLATE OF NONCONDUCTIVE MATERIAL; CHARGING-ELECTRODE MEANS FOR SAID LAYER INCLUDING A PLURALITY OF ELONGATED CONDUCTORS DISPOSED CLOSE TO SAID PATH BUT SEPARATED THEREFROM BY SAID PLATE; AND FEED MEANS INCLUDING A ROLLER JUXTAPOSED 